A processor core, also known by the name CPU board, is an embedded electronic board comprising a processor carrying out calculations and processing operations. By way of example, a processor core can notably be embedded in a system of aircraft type where it performs a set of specific numerical calculations. A processor core, particularly in the aeronautical sector, carries out tasks of great criticality, such as for example managing the flight parameters, and must consequently exhibit significant reliability. To meet these constraints, a processor core is defined by a detailed and validated specification, and must form the subject of a validation/certification phase both from the conceptual and the hardware standpoint. It therefore follows notably that each modification of a characteristic of said processor core must form the subject of an upgrade of the specification followed by a study of risk and/or impact with regard to its reliability and those of the related equipment. It should of course be noted that such studies have a significant impact on the cost of the processor core.
In this context, one of the characteristics of a processor core liable to modification not only in the design phase but also in the course of the life cycle of said core is the frequency of the components included in the processor core. Modification of the frequency of the components included in the processor core is generally designated by the term “Throttling/Unthrottling” of a processor core. Furthermore, in relation to the above stated constraints, it is desirable that the “Throttling/Unthrottling” of the processor core be able to be performed without hardware modification (“without Hardware retrofit”).
In order to carry out “Throttling/Unthrottling” of a processor core, it is known to include in the latter frequency multiplier components (PLL), and/or clock pilots comprising pull-up/pull-down clock drivers. Unfortunately, a hardware update (“retrofit”) is inevitable to carry out the change of frequency of the processor core. This results notably in the impossibility of a dynamic change (that is to say while operating) of configuration, as well as the drawbacks set forth above.
In the computing sector, in particular that of personal computers, the basic input/output systems (BIOS) can in certain cases be provided with a device integrated into the motherboard making it possible to change the processor frequency and the bus frequency. However this solution does not exhibit characteristics of sufficient security and reliability for an embedded processor core. Specifically, if an erroneous value is written via the BIOS before the computer is restarted, the latter will be incapable of starting up again and will be in an unstable and unpredictable state.